1892.] NEW SPECIES OF EARTHWORMS. 145 



records are scanty. In Qriodrilus I mentiou ^, briefly, tlie " hemi- 

 spherical gland, which may be called a prostate," and which "con- 

 sists of cells similar to those forming the epidermis of the clitellum 

 and quite continuous with them ; the gland appears to be formed 

 only by a hemispherical thickening of the epidermis over this area." 

 Rosa ^ refers to this organ as " atrium." In the case of Callidrilus, 

 Michaelsen^ states that this "doubtful prostate" consists of small 

 granular cells, with indistinct boundaries, the nuclei sometimes being 

 scarcely recognizable ; in the same place he describes — though very 

 bi'iefly — structures of the same nature as those in Micr. papillata 

 as occurring in Kynotus madagasoariensis ; to which I shall refer 

 later on in this paper. 



The nature of the organ in Oeoscolex is unknown. But Micro- 

 chceta (and probably Kynotus) differs from the rest in that this 

 gland is entirely independent of the sperm-duct ; whereas in pros- 

 tatiferous worms (that is, those of the families Gryptodrilidee, 

 PerichcetidcB, Acanthodrilidce, EudrilidcB, &c.) this gland is always 

 in connection with the sperm-duct, or in its immediate neighbourhood ; 

 moreover, it is tubular in genei'al character and is apparently a more 

 efficient organ of copulation than in these other cases. 



We are in ignorance of the real function of the prostate or of the 

 " genital duct " in these prostatiferous worms; but there is, pro- 

 bably, a protrusion of the muscular duct during copulation, and an 

 insertion thereof into the spermatheca, as there is undoubtedly 

 in such forms as the Tubificidce : but in the case of Microchceta 

 such a penial function is inapossible, for there is no sac into 

 which such a papilla could be inserted ; it probably, however, 

 serves as a sucker. The small papilla in the terminal pit of the 

 larger one, the muscular arrangements, and the folded cavity suggest 

 such a sucking-organ ; and, no doubt, the copulating chsetae serve to 

 aid this apparatus in holding on to another worm *. 



It is not necessary to think that this sucking-apparatus in Micro- 

 cJidbta is the forerunner of the prostates with their protrusible duct, 

 though it is quite possible that this latter organ may have arisen 

 from some such apparatus as is present in Bmchydrilus, Geoscolex, 

 &c., where the "sucker" is perforated by the sperm-duct. During 

 copulation in Lumbricus, &c., the ventral surface of the clitellum 

 itself, bounded by the tubercula pubertatis, very probably acts as 

 a sucker ; here in Microchceta a more specialized apparatus, on 



^ " Studies in Earthworms, III.," Q. J. M. Sc. xxvii. p. 568. 



^ "Sul Criodrilus lacuum," Mem. d. R. Accad. d. 8ci. d. Torino, ser. 2, 

 tom. xxxviii. 



3 " Terricolen d. Eerliner Zool. Samml.," Arch. f. Naturgeseh. 1891. 



^ Eosa describes (Ann. d. k. k. Natur. Hofmus. 1891) certain glandalar 

 bodies in M. benhami (in somif;es xi. to xxviii.) which appear to bave a some- 

 what similar structure ; but be mentions no external papilla : be compares 

 tbem with tbe " pyriform glands " of Urobenus and Urochceta, and suggests, as 

 I bave done, tlieir possible connection witb tbe prostates of other worms ; and 

 his species forms an interesting link between tbe arrangement in Urobenus and 

 M. papillata, tbougb tbe structures in M. benhami do not appear to have any 

 copulatory functions. 



Proc. Zool. Soc— 1892. No. X. 10 



